"I start my duties at a daunting time in international affairs -- starting from Darfur [Sudan] to [the] Middle East, Lebanon, Iran, Iraq, North Korea -- many other crises that trouble our world," Ban said.

Ban also told staffers that the UN remains an important body addressing global challenges and issues.

The 62-year-old South Korean diplomat officially took over as UN chief, replacing Kofi Annan, on January 1.

The eighth secretary-general in the history of the United Nations, he has pledged to work to strengthen the UN's three main areas of focus -- security, development, and human rights -- to help make the world more peaceful and prosperous.